1. Field of the Invention
The present invention relates to an exhaust gas temperature control method, an exhaust gas temperature control apparatus, and an internal combustion engine system for controlling the temperature of exhaust gas discharged from an internal combustion engine.
2. Background Information
There are various known technologies for purifying an exhaust gas discharged from an engine using an exhaust gas purification device installed in an exhaust passage. For example, there are diesel particulate filters (DPF) that capture particulate matter (PM) discharged from diesel engines, and NOx trapping catalytic converters that trap nitrogen oxides (NOx) contained in the exhaust gas when the air fuel ratio of the exhaust gas is lean and clean and release the nitrogen oxides when the air fuel ratio of the exhaust gas is rich. When a diesel particulate filter continuously captures particulate matter, it eventually becomes clogged. Also, a NOx trapping catalytic converter becomes contaminated with sulfur over time due to the sulfur components exhausted from the engine. Therefore, the diesel particulate filter is regenerated by raising the temperature of the exhaust gas such that the accumulated particulate matter is combusted and removed. Similarly, the NOx trapping catalytic converter is regenerated by raising the temperature of the exhaust gas such that the sulfur contamination is removed.
For example, Japanese Laid-Open Patent Application Publication No. 2005-42715 proposes a method for raising the exhaust gas temperature by retarding (delaying) the timing of a fuel injection for a main combustion.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved exhaust gas temperature control method, exhaust gas temperature control apparatus and internal combustion engine system. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.